There is disclosed for example in Patent Literature 1 measurement of surface potentials of a toner particle included in a toner using a scanning probe microscope. Specifically, Patent Literature 1 discloses that the average value of surface potentials of the toner particle is set to be at least −3.0 V and no greater than −0.5 V and a region having a minus potential is set to occupy 95% or more of a surface region of the toner particle. Furthermore, a toner producing method disclosed in Patent Literature 1 uses a charge control agent (calixarene) for adjusting the chargeability of the toner.